Fluorescent aryl 3,3-pyrazolyl-2-pyrazolines

ABSTRACT

WHEREIN R1 - R4 independently represent a hydrogen atom, alkyl, or aralkyl group and R5 and R6 independently represent an aryl group.   D R A W I N G Aryl-3,3&#39;&#39;-pyrazolyl-2-pyrazolines are found to fluoresce when irradiated with ultraviolet light. These compounds have the generic formula:

United States Patent 11 1 Pearson 1 1 3,883,549 [4 1 May 13,1975

1 1 FLUORESCENT ARYL 3,3-PYRAZOLYL-2-PYRAZOLINES [75] Inventor: Ian Pearson, Harlow, England [73] Assignee: Minnesota Mining and Manufacturing Company, St. Paul, Minn.

22 Filed: Feb. 5, 1973 21 Appl. No.: 329,328

[30] Foreign Application Priority Data Feb. 10, 1972 United Kingdom 6384/72 [52] US. Cl. 260/310 D; 117/33.5 T; 252/3013 W; 260/310 H; 260/310 R [51] Int. Cl C07d 49/28 [58] Field of Search 260/310 D [56] References Cited OTHER PUBLlCATiONS Finar, J. Chem. Soc. (London), 1961, pp. 674-679.

Finar et al., 11, .1. Chem. Soc. (London), 1959, pp. 1819-233.

Primary Examiner-Nata1ie Trousof Attorney, Agent, or FirmAlexander, Sell, Steldt & DeLaHunt [57] ABSTRACT Aryl-3,3'-pyrazo1y1-2-pyrazo1ines are found to fluoresce when irradiated with ultraviolet light. These compounds have the generic formula:

wherein R R independently represent a hydrogen atom, alkyl, or aralkyl group and R and R independently represent an aryl group.

7 Claims, No Drawings FLUORESCENT ARYL Preferably the organic base is an aromatic com- 3,3-PYRAZOLYL-Z-PYRAZOLINES pound, e.g., one containing a tertiary nitrogen atom.

Suitable bases are the pyridines, pyridine itself being This invention relates to fluorescent pyrazolmes and preferred. To avoid quaternization of the pyridine durto their preparation and use as fluorescent materials. ing reaction, pyridines blocked in the 2-position by According to the invention there is provided an arylsuitable substituents, e.g., 2,6-lutidine, can be used. 3,3-pyrazolyl-2-pyrazoline having the general formula: Preferably a single l-aryl-pyrazolidin-3-one is reacted with the phosphorous oxychloride to give a l c C C 1 CH 3 pyrazoline in which R and R R and R, and R and u 3 3' it R are identical with one another, although reacting a I mixture of l-aryl-pyrazolidin-3-ones can give pyrazo- C l 2 N l 5 lines in WhlCl'l R and R, R and R and R and R dif- R N u fer from one another.

I I The reaction occurs as illustrated in the following R R general reaction scheme:

in which R to R each independently represent a hy- 0 drogen atom or an alkyl (preferably one containing E C from 1 to 4 carbon atoms) or aralkyl group, and R and R each independently represents an aryl 2 I CH NH POCH3 group. The aryl groups used in the practice of this R N invention, including those in the aralkyl moieties, I pyridine are phenyl and naphthyl, or phenyl and naphthyl R having one or more substituents such as alkyl, aralkyl, alkoxy, alkylthio, carboxy, carbalkoxy, halo- 1 1 gen, amino, cyano, etc. Preferably the alkyl groups R in these moieties contain 1 to 4 carbon atoms. C C CH Preferably R and R, R and R and R and R are 1'; c': each identical so that the general formula is in effect: l l 2/ N N z -c-c---c--cH H II II I R R 0 R2/ 0 N N N N CH R2 R1 CH c I C1 v 5 5 R R 2 Cir N in which R, R and R are as defined above. 40 R N' These pyrazoline compounds according to the inven- 5 tion fluoresce when irradiated. Generally they show a R powerful blue-green fluorescence when irradiated with ultra-violet light, e.g., of wavelengths of from 300 to 450 mu. These compounds are therefore useful as, for example, optical brightening agents and fluorescent pigments.

According to another aspect of the invention these aryl-3,3'-pyrazolyl-2-pyrazoline compounds can be prepared by reacting under anhydrous conditions at 5 As can be seen some 3-chloro-l-aryl-2-pyrazoline is produced as a by-procluct. This can readily be separated from the required pyrazoline according to the invention by extraction with boiling methanol.

The 3-chloro-l-aryl-2-pyrazoline formed as a byproduct is an example of certain of the 3-chloro-1-aryl- 2-pyrazolines which have the general formula:

least one l-aryl-pyrazolidin-3-one having the general ll formula: I 7 /C1 R 0 0 R 0 a cn o R N ctr NH 15/ N 2 i i l R D 6O R m whlch R to R each independently of each other represents a hydrogen atom or an alkyl, aralkyl or in which R R and R are as defined above, aryl, and represents an aryl group, Preferably a with phosphorus oxychloride in the presence of an orphenyl p y g p which y be Substiganic base. After completion of the reaction, the reactuted in one or more Positions y radicals Such 35 tion mixture can be neutralized to give an insoluble a halogen atom or an alkyl, alk xy or alkylthio precipitate of the desired compound. This can then be group as described in copending United Kingdom purified by recrystallization. Patent Application No. 6383/72.

The invention will now be illustrated by the following Examples.

EXAMPLE 1 1,1 '-Diphenyl-3 ,3 -pyrazo1yl-2-pyrazoline 1-Pheny1pyrazolid-3-one (50g) was dissolved in pyridine (200 ml), the solution cooled in ice and phosphorus oxychloride (54 g) then dropped in over a period of 30 minutes. After allowing the reaction mixture to reach room temperature it was left to stand for 1 hour and then heated on the steam bath for a further 2 hours, after which time it was poured onto 2 kilograms of crushed ice.

After neutralization of the pyridine with hydrochloric acid a grey precipitate was filtered off, well washed with water and dried to give a solid (36 g). This solid was then purified by dissolving in toluene, boiling the resulting solution with charcoal for 5 minutes, and then removing the charcoal by filtration. Upon cooling the toluene solution deposited yellow needles having a powerful green fluorescence.

Further purification was effected by boiling these crystals with methanol to remove any residual 3- chloro-l -phenyl-2-pyrazoline.

The yield was 11.2 g of a solid with a melting point of 196C and a maximum fluorescence emission in chloroform at 434 mu.

Analysis Calculated for C H N C 74.97; H 5.59; N 19.43;

Found C 75.35; H 5.30; N 19.63.

EXAMPLE 2 4,4'-Dimethyl- 1 ,1 -diphenyl-3,3 -pyrazolyl-2- pyrazoline 4-Methyl-l-phenylpyrazolid-3-one (54 g) was dissolved in 2,6-lutidine (200 ml), the solution in ice and phosphorus oxychloride (54 g) added over a period of 30 minutes. The mixture was then allowed to stand for 1 hour at room temperature, followed by heating for 2 hours on the steam bath. Upon pouring onto ice and neutralizing with hydrochloric acid, a stiff grey gum as precipitated. This gum was extracted with boiling toluene, followed by treatment of the resulting toluene solution with charcoal and filtration. The toluene was distilled off and the residue recrystallized from ethanol to give a yellow crystalline solid (7.5 g; melting point 148C) having a strong blue fluorescence with a maximum emission in chloroform at 430 mu Analysis Calculated for C H N C 76.0; H 6.3; N 17.7; Found C 75.83; H 6.9; N 16.7.

EXAMPLE 3 1,1Di-(p-chlorphenyl)-3,3-pyrazolyl-2pyrazoline 1-p-Chlorophenylpyrazolid-3-one g) was dissolved in pyridine (200 ml), cooled in an ice bath and phosphorus oxychloride (27 g) dropped in over a period of 30 minutes. The mixture was then left for 1 hour at room temperature and finally heated on the steam bath for 2 hours. Upon pouring onto 1 kilogram of ice and neutralizing to pH 7 with hydrochloric acid, a red solid was precipitated, filtered off, washed with water and dried (13.5 g). This solid was then boiled with a mixture (200 ml) of equal parts of methanol and water. The insoluble material was filtered off, dried and recrystallized from toluene to give a fluorescent yellow solid (4 g; melting point 237C). Analysis Calculated for C H N C1 C 60.53; H 3.95; N 15.68; Cl Found C 60.3; H 4.00; N 15.52; Cl 19.6

EXAMPLE 4 1,1 '-Di-(p-tolyl)-3,3 -pyrazolyl-2pyrazoline l-p-Tolyl-pyrazolidin-3-one (19.2 g) was treated as in Example 1 with phosphorus oxychloride (25 ml) and pyridine ml). Purification of the reaction mixture as in Example 1 gave 1,1'-di-(p-tolyl)-3,3'-pyrazo1yl-2- pyrazoline (5.4 g) as yellow plates (melting point 236.6C) being strong blue fluorescence with a maximum emission in chloroform at 460 mu. Analysis Calculated for C H N C 76.00; H 6.37; N 17.71; Found C 76.19; H 6.40; N 17.94.

EXAMPLE 5 5,5 '-Dimethyl- 1 ,1 '-diphenyl-3 ,3 -pyrazolyl-2- pyrazoline 5-Methyl-1-phenyl-pyrazolidin-3-one (5.0 g) was treated with phosphorus oxychloride (16 ml) and 2,6- lutidine (25 m1) as in Example 2. Purification of the reaction mixture as in Example 2 gave 5,5'-dimethy1- 1,1 '-diphenyl-3,3-pyrazolyl-2-pyrazoline (1.0 g) as yellow crystalline plates (melting point 169C) having a strong blue fluorescence with a maximum emission in chloroform at 440 mu. Analysis Calculated for C H N C 76.00; H 6.37; N 17.71; Found C 74.34; H 6.43; N 17.48.

EXAMPLE 6 l, l -Di-(p-anisy1)-3,3 '-pyrazolyl-2-pyrazoline 1-p-Anisyl-pyrazolidin-3-one (3.8 g) was treated as in Example 1 with phosphorus oxychloride (2.5 m1) and pyridine (20 m1). Purification of the reaction mixture as in Example 1 gave 1,1 '-di-(p-anisyl)-3,3- pyrazolyl-2-pyrazoline as fluorescent yellow plates from toluene (0.8 g; melting point 266C).

Analysis Calculated for C H N O C 68.9; H 5.80; N 16.1; Found C 67.6; H 5.80; N 16.1.

Since all of these compounds as prepared in the above Examples fluoresce strongly when irradiated with ultraviolet light, they are useful in such applications as optical brightening agents and fluorescent pigments.

1 claim:

1. An aryl-3,3 '-pyrazolyl-2-pyrazoline of the formula:

wherein R to R" independently represent hydrogen or alkyl with up to 4 carbon atoms, and

R and R independently represent phenyl or naphthyl which may be substituted with one substituent from the group of halogen, alkyl with up to 4 carbon atoms, alkoxy with up to 4 carbon atoms, and alkylthio with up to 4 carbon atoms.

2. An aryl-3,3'-pyrazolyl-2-pyrazoline having the for- R and R independently represent phenyl or naphmula: thyl which may be substituted with one substituent 1... C C C CH l 3 from the group of halogen, alkyl with up to 4 car- I bon atoms, and alkoxy with up to 4 carbon atoms.

5 3. 1,1'-Diphenyl-3,3'-pyrazolyl-2-pyrazoline.

C N N CH 4. 4,4-Dimethyl-l,l '-diphenyl-3,3-pyrazolyl2- R pyrazoline.

2 I l 5. 1,1'-Di-(p-chlorphenyl)-3,3'-pyrazolyl-pyraz0line.

R R 6. 1,1'-Di-(p-tolyl)-3,3-pyrazolyl-2-pyrazoline.

5 6 l0 7. 5,5'-Dimethyl-l,l '-diphenyl-3,3-pyrazolyl-2- wherein R to R independently represent hydrogen pyrazoline or alkyl with up to 4 carbon atoms, and 

1. AN ARYL-3,3''-PYRAZOLYL-2-PYRAZOLINE OF THE FORMULA:
 2. An aryl-3,3''-pyrazolyl-2-pyrazoline having the formula:
 3. 1,1''-Diphenyl-3,3''-pyrAzolyl-2-pyrazoline.
 4. 4,4''-Dimethyl-1,1''-diphenyl-3,3''-pyrazolyl2-pyrazoline.
 5. 1,1''-Di-(p-chlorphenyl)-3,3''-pyrazolyl-pyrazoline.
 6. 1,1''-Di-(p-tolyl)-3,3''-pyrazolyl-2-pyrazoline.
 7. 5,5''-Dimethyl-1,1''-diphenyl-3,3''-pyrazolyl-2-pyrazoline. 